Funds are requested to purchase a JEOL 1200 EX electron microscope to be housed in the EM facility of the Department of Anatomy. This instrument would be devoted primarily to studies of serial sections in analyzing: 1) local neuronal circuits in mammalian brain 2) regeneration of identified neural circuits in vertebrate spinal cord 3) macromolecular organization of the myosin filament. The technical features of the new instrument critical to these purposes are: 1) high accelerating voltage (120KV) 2) excellent performance at low magnification (approximately 1500X) as well as high magnification (10,000-100,000X) 3) advanced aids to critical focusing 4) microprocessor controlled realignment for efficient switching between different magnifications (for efficient time sharing by different users) 5) video system to permit scanning at low beam intensities (to minimize beam damage and contamination during search for corresponding regions of serial sections and during alignment of serial sections for photography) 6) capability of rotating and tilting the sections in the column (for alignment during photography and for producing stereo pairs of critical structures) 7) automatic montage photography. The instrument would also serve other members of the department in studies of motility and cell differentiation The proposed instrument would replace a 15 year old instrument in the Department of Anatomy which is technologically obsolete and increasingly unstable and unreliable.